EGR Malfunction

[orezok]

2000 camry 4 cyl 150K miles. The engines started pinging recently, not only under load, but on level roads at 75, NOT an octane issue- already tried that. No MIL codes.

Determined that EGR system is not functioning properly. EGR valve, vacuum modulator, vacuum switching valve and hoses all check OK per factory manual tests.

Found that VSV is receiving 12v at all times. It should de-energize at high RPM to allow full vacuum to EGR valve.

Bad ECU or?

[hooRAH]

Originally Posted by orezok

No MIL codes.

Determined that EGR system is not functioning properly.

How?

[71Corolla]

^^ Was wondering the same thing.

BTW, if I'm understanding the service manual correctly, if the VSV is always getting 12 volts, then the EGR valve will never open and a CEL will show.

[orezok]

The EGR never gets high vacuum at high RPM (test with gauge while driving). The VSV always has 12v (test with gauge). No MIL's, that's why I'm thinking ECU malfunction.

[71Corolla]

I see what you're saying. I would replace the ECU as a last resort though. I think it is much more likely that some other problem is causing the VSV to always have 12 volts (which closes off air flow and will prevent the EGR from ever opening)

I'm not sure what conditions the ECU is looking for before it cuts power to the VSV. I know that RPM and engine temperature are factored in, but not sure if there are other conditions it looks for.

[orezok]

Three conditions are required to activate high RPM VSV activation. Temp above 130, distributor input and vacuum. I put my computer based scan tool on and it is reporting out the correct temperature from the temperature sensor, the correct RPM (distributor input), but I don't know where the vacuum signal to the ECM is generated. Most likely from the manifold pressure sensor. I'll do some research on this one tonight and see if that is an issue.

Given that the engine is running perfectly, none of the 3 should be deficient. Trumping the whole situation again is that no MIL codes are being stored.

Could still be a bad ECM, but I'll keep looking.

[71Corolla]

^^ post back with your findings.

[Hajoca]

Is hte EGR air filter dirty, and does the EGR piston move freely?

[orezok]

Originally Posted by 71Corolla

^^ post back with your findings.

Thought it was a bad MAP sensor, but I did a bad test (vacuum leak in mu pump). Still looks like ECM.